The invention relates to a star scalper for separating supplied material, comprising a number of parallel, rotatable shafts that are each equipped with a number of star bodies placed at a distance from each other, which bodies have a hub and radially protruding star fingers, in which the star bodies of each shaft extend between the star bodies of the adjacent shaft.
Such a scalper is known and for instance meant for sifting waste, in which the waste has to be separated in a crude and fine fraction. There is a certain distance between the extremities of the fingers of the one star body on one shaft and the hub of the star wheels in between which the one star body has to rotate on the adjacent shaft, which distance together with the intermediate distance between two consecutive star bodies on the adjacent shaft determine a rectangular passage. Said rectangular passage is normative for the size of the objects which are let through by the star scalper. The star fingers of the star scalper move along each other with small intermediate distance. Usually the shafts of the star scalper all rotate in the same direction, so that the material moves over the scalper and the fraction which is left on the scalper is discharged. In this way it is also effected that an object which is too large for the passage will not block the passage, because in every passage a star body is present which makes an upward movement, so that the object is released.
A disadvantage of the known star scalper is that fine material into the fine fraction may cake onto the hubs of the star bodies, as a result of which the effective passage is made narrower. In this way the sifting effect of the star scalper is reduced after some time. The star scalper also has to be cleansed regularly.
It is an object of the invention to provide an improved star scalper.